CN110923582A - Carbon manganese chromium system hot-rolled ribbed steel bar with effective boron not less than 96% and preparation method thereof - Google Patents
Carbon manganese chromium system hot-rolled ribbed steel bar with effective boron not less than 96% and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
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- C22C33/04—Making ferrous alloys by melting
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention belongs to the technical field of ferrous metallurgy and steel rolling, and particularly relates to a carbon-manganese-chromium hot-binding band rib steel bar with effective boron of not less than 96% and a preparation method thereof. The invention aims to solve the technical problem of providing a carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron of not less than 96 percent and a preparation method thereof. The steel bar comprises the following chemical components in percentage by weight: c: 0.21% -0.25%, Si: 0.50-0.70%, Mn: 1.40-1.60%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Cr: 0.30-0.50%, Ti: 0.010% -0.020%, B: 0.0008 to 0.0030 percent, and the balance of Fe and inevitable impurities. The product prepared by the method ensures the stability and hardenability of steel and has good mechanical property.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy and steel rolling, and particularly relates to a carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron of not less than 96% and a preparation method thereof.
Background
Boron steel has good hardenability, and the hardenability of the steel can be greatly improved by adding 0.0005 to 0.0030 percent of trace boron. However, boron-containing steel is a steel grade which is extremely difficult to smelt and has the largest performance fluctuation, because the addition amount of boron is very small, the boron is an alloy element which is known to be added to steel in the smallest amount per ton, the affinity of boron with oxygen and nitrogen is strong, and the addition of boron is easy to oxidize, so that the accurate control of the boron content in a certain range is very difficult.
Boron exists in five forms in steel, namely solid solution boron (B solid), Boron Nitride (BN), Boron Oxide (BO)X) Iron-boron cementite [ Fe ]3(CB)]And iron boron acid compound [ Fe23(CB)6]I.e. all B ═ B solid + B [ Fe3(CB)]+B[Fe23(CB)6]+B[BN]+B[BOX]. Wherein, boron in the boron nitride and the boron oxide is acid insoluble boron which is not beneficial to the hardenability of the steel and is ineffective boron; the ferroborocementite and the ferroboron acid compound are boron phases, and boron and solid solution boron in the boron phases are soluble in acid and are acid soluble boron, namely effective boron. Therefore, even if the content of boron in steel can be accurately controlled, the influence of the presence form of different boron on the properties of boron steel greatly fluctuates.
In order to adapt to the continuous and rapid production rhythm of steel, chemical component analysis equipment of a steel mill is a spectrometer at present, a spectrum analysis method cannot distinguish various existing forms of boron, analysis results of boron elements are all boron, and the analysis results are meaningless for guiding the production of boron steel because only acid-soluble boron is effective boron and all boron is not equal to the acid-soluble boron. Chemical analysis can basically determine the content of boron in various forms, and chemical analysis cannot rapidly obtain results, so that the method is difficult to apply to actual production.
Therefore, the difficulty in boron steel production is mainly reflected in that the existence form of boron in steel types cannot be accurately controlled in the smelting process, and effective boron in steel is difficult to accurately quantify through a rapid detection means, so that boron steel production and hardenability control cannot be guided, and the performance difference is large under the condition of equivalent chemical components, which is also a main reason that boron steel is difficult to popularize.
Patent document CN102796962A discloses "niobium-titanium-boron microalloy HRB600 high-strength aseismic steel bar and preparation thereof", which is obtained by molten steel smelting, molten steel casting, controlled rolling and controlled cooling of steel billet, and has the following mass percentages: c: 0.14 to 0.18 wt%, Si: 0.30-0.50 wt%, Mn: 0.50-0.75 wt%, Cr: 0.50-0.70 wt%, Nb: 0.030 to 0.050 wt%, B: 0.0015-0.0030 wt%, Ti: 0.020-0.040 wt%, S is less than or equal to 0.045 wt%, P is less than or equal to 0.045 wt%, and the balance is Fe and inevitable impurities. In the preparation method, ferroniobium needs to be added to obtain the required niobium content, but the niobium content of steel can cause a casting blank to generate stronger crack tendency and deteriorate the surface quality of the casting blank, and the ferroniobium is expensive and has high production cost; in addition, in the method, the alloying of Ti and B is directly added into the molten steel, the yield fluctuation is large (Ti and B are easily oxidized elements), and the precise control of the components is not facilitated.
Patent document CN101654761A discloses "carbon-manganese series composite microalloyed steel for engineering machinery and a preparation method thereof", wherein the chemical components of the carbon-manganese series composite microalloyed steel prepared by the patent method are as follows by weight percent: 0.32-0.37% of C, 0.15-0.30% of Si, 1.20-1.40% of Mn1, less than or equal to 0.030% of P, less than or equal to 0.030% of S, 0.0005-0.0030% of B, 0.10-0.60% of Cr0.01-0.07% of Al, 0.01-0.06% of Ti0.01-0.06% of Fe and trace impurities. The content of effective boron in the steel is not lower than 95%, and Ti/N is controlled to be 3-6, so that boron in the steel is basically all effective boron. The method needs to add a certain amount of aluminum for deep deoxidation, has high Al content and poor molten steel castability, and is easy to block a water gap in the continuous casting process.
Disclosure of Invention
The invention aims to solve the technical problem of providing a carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron of not less than 96 percent and a preparation method thereof.
The invention provides a carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron not less than 96%, which comprises the following chemical components in percentage by weight: c: 0.21% -0.25%, Si: 0.50-0.70%, Mn: 1.40-1.60%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Cr: 0.30-0.50%, Ti: 0.010% -0.020%, B: 0.0008 to 0.0030 percent, and the balance of Fe and inevitable impurities.
Wherein, in the carbon manganese chromium hot-rolled ribbed steel bar with the effective boron of not less than 96 percent, the microstructure of the steel bar is ferrite and pearlite, and the grain size of the ferrite is more than or equal to 11 grade.
Furthermore, the yield strength of the steel bar is more than or equal to 410MPa, the tensile strength is more than or equal to 550MPa, the elongation after fracture is more than or equal to 25%, the maximum total elongation is more than or equal to 13%, and the yield ratio is more than or equal to 1.30.
The invention also provides a preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron of not less than 96%, which comprises the following steps: pre-desulfurizing molten iron, smelting, alloying, LF refining, continuously casting small square billets, heating steel billets, rolling and cooling to obtain the alloy steel; the titanium wire is fed in the early stage of LF refining, the boron wire is fed in the later stage of LF refining, the content of Ti in the molten steel is controlled to be 0.010-0.020%, the content of B in the molten steel is controlled to be 0.0008-0.0030%, and the effective boron is more than or equal to 96%.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron content of not less than 96%, the molten iron comprises the following chemical components in percentage by mass: c: 4.00 to 4.40 percent of Si, less than or equal to 0.30 percent of Mn, less than or equal to 0.30 percent of Cr and less than or equal to 0.10 percent of Cr.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron content of not less than 96%, smelting is carried out until the content of C in molten steel is not more than 0.06%; tapping with P content less than or equal to 0.045% and S content less than or equal to 0.045%.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron of not less than 96%, the heating temperature of the steel billet is 1100-1200 ℃; the soaking temperature is 1140-1230 ℃; the total time of heating and soaking is 80-160 min.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron content of not less than 96%, the rolling is performed by 6 times of rough rolling, 6 times of medium rolling and 6 times of finish rolling; the finish rolling temperature is controlled at 920-1000 ℃, and water is not penetrated after finish rolling.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron of not less than 96%, the cooling is carried out by adopting a cooling bed, the temperature of the cooling bed is 920-980 ℃, and the cooling bed is naturally cooled to be below 200 ℃.
In the preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with the effective boron content of not less than 96%, the specification of the steel bar is phi 12 mm-phi 32 mm.
The invention has the beneficial effects that: according to the method, a proper amount of titanium wires are fed in the early stage of LF furnace refining, a proper amount of boron wires are fed in the later stage of LF furnace refining, the content of Ti in the molten steel is controlled to be 0.010-0.020%, the content of B in the molten steel is controlled to be 0.0008-0.0030%, the effective boron content is more than or equal to 96%, and the stability and the hardenability of the steel are ensured. The method utilizes the effect of improving hardenability by compounding chromium and effective boron to replace expensive V or Nb microalloy elements to produce the 400 MPa-level hot-rolled ribbed anti-seismic reinforcing steel bar, is simple, and obviously reduces the microalloying cost. The yield strength of the steel bar prepared by the method is more than or equal to 410MPa, the tensile strength is more than or equal to 550MPa, the elongation after fracture is more than or equal to 25%, the total elongation of the maximum force is more than or equal to 13%, the yield ratio is more than or equal to 1.30, the microstructure is ferrite and pearlite, the grain size of the ferrite is more than or equal to 11 grade, and the steel bar has good mechanical properties. The method solves the problems of cost increase and poor surface quality of the casting blank caused by adding ferroniobium, ensures the element yield by adding Ti and B by adopting a wire feeding process, and has good castability of molten steel because certain Al content is not required in steel.
Detailed Description
The invention aims to provide a carbon manganese chromium hot-rolled ribbed steel bar with effective boron of not less than 96 percent and a preparation method thereof, wherein the microstructure of the steel bar is ferrite and pearlite, the grain size of the ferrite is more than or equal to 11 grade, the yield strength is more than or equal to 410MPa, the tensile strength is more than or equal to 550MPa, the elongation after fracture is more than or equal to 25 percent, the total elongation at maximum force is more than or equal to 13 percent, and the strength-to-yield ratio is more than or equal to 1.30.
Specifically, the invention provides a carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron not less than 96%, which comprises the following chemical components in percentage by weight: c: 0.21% -0.25%, Si: 0.50-0.70%, Mn: 1.40-1.60%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Cr: 0.30-0.50%, Ti: 0.010% -0.020%, B: 0.0008 to 0.0030 percent, and the balance of Fe and inevitable impurities.
The mechanism and the action of each component of the invention are as follows:
b is an element for strongly enhancing the hardenability of steel, and the hardenability of steel can be improved by times by adding 0.0005 to 0.0030 percent of trace boron. However, boron-containing steel is extremely difficult to smelt and has the largest performance fluctuation, because the addition amount of boron is very small, the boron is an alloy element which is added to steel per ton in the known steel at the least, the affinity of boron and oxygen is very strong, and the boron addition is easily oxidized, so that the accurate control of the boron content in a certain range is very difficult. The existing forms of boron in the steel are effective boron and ineffective boron, only the effective boron is beneficial to the hardenability of the steel, and the hardenability of the steel can be multiplied. In the invention, the addition of B is controlled to be 0.0008-0.0030 percent, wherein the effective boron stability is controlled to be more than or equal to 96 percent.
C is the most basic strengthening element in steel, the yield strength of the steel bar is increased by about 10MPa and the tensile strength is increased by about 14MPa when the content of C in the steel bar is increased by 0.01 percent, and the excessively high C can reduce the shaping and weldability of the steel bar, and in the invention, the content of C is in the range of 0.21 to 0.25 percent.
Si is an important deoxidizer which is helpful for reducing the oxygen content in steel and reducing inclusions, and simultaneously Si is a ferrite strengthening element which can improve the strength of ferrite through solid solution strengthening, and in order to ensure that the steel bar has a lower oxygen content, the Si content ranges from 0.50% to 0.70%.
Mn is a good deoxidizer and a desulfurizer, mainly plays a role in solid solution strengthening in steel, is an important toughening element, has an obvious effect of improving the tensile strength of steel compared with the effect of improving the yield strength, and has a Mn content range of 1.40-1.60% in the invention in order to ensure that a steel bar has good oxygen and sulfur indexes.
P and S are harmful impurity elements in the steelmaking process, harmful inclusions are easily formed in steel, the toughness and the shape of the steel are reduced, P is easily segregated at a grain boundary, the brittleness of the steel is increased, and the content ranges of P and S are less than or equal to 0.045%.
Cr is a strong hardenability element, the hardenability of the steel can be obviously improved by adding the Cr into the steel, the strength and the hardness of the steel are improved, the hardenability of the steel containing the Cr can be doubled by adding the Cr and effective boron, and the range of the Cr content is 0.30-0.50 percent in the invention.
Ti is a good element for fixing oxygen and nitrogen, can combine with oxygen to generate titanium dioxide, can combine with nitrogen to produce titanium nitride, and after a proper amount of titanium is added to combine with oxygen and nitrogen in steel, a good condition can be created for alloying boron in steel, so that boron oxide or boron nitride is avoided, and stable effective boron is obtained for ensuring boron alloying.
The invention also provides a preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron of not less than 96%, which comprises the following steps: pre-desulfurizing molten iron, smelting, alloying, LF refining, continuously casting small square billets, heating steel billets, rolling and cooling to obtain the alloy steel; the titanium wire is fed in the early stage of LF refining, the boron wire is fed in the later stage of LF refining, the content of Ti in the molten steel is controlled to be 0.010-0.020%, the content of B in the molten steel is controlled to be 0.0008-0.0030%, and the effective boron is more than or equal to 96%.
The key of the method of the invention is that: the method comprises the steps of feeding a proper amount of titanium wires in the early stage of LF furnace refining, adjusting Ti to a proper level, feeding a proper amount of boron wires in the later stage of LF furnace refining, controlling the content of Ti in the molten steel to be 0.010-0.020% and controlling the content of B in the molten steel to be 0.0008-0.0030%, wherein the content of effective boron is more than or equal to 96%, and strictly controlling the content of trace element B to ensure that the content of effective boron is more than or equal to 96%, so that the stability and the hardenability of steel are ensured. The invention utilizes the effect of improving hardenability by compounding chromium and effective boron to replace expensive V or Nb microalloy elements to produce 400 MPa-level hot-rolled ribbed anti-seismic reinforcing steel bar, the yield strength of the reinforcing steel bar is more than or equal to 410MPa, the tensile strength is more than or equal to 550MPa, the elongation after fracture is more than or equal to 25%, the maximum total elongation is more than or equal to 13%, the yield ratio is more than or equal to 1.30, the microstructure is ferrite and pearlite, the ferrite grain size is more than or equal to 11 levels, and the specification comprises phi 12 mm-phi 32 mm.
The present invention will be further illustrated by the following specific examples.
The compositions of examples 1-3 and comparative examples, in weight percent, are shown in Table 1, with the balance being Fe.
Table 1 compositions (wt.%) of reinforcing bars of examples 1 to 3 and comparative example
| Item | C | Si | Mn | P | S | V | Cr | Ti | B |
| Comparative example | 0.23 | 0.60 | 1.50 | 0.015 | 0.017 | 0.035 | － | － | － |
| Example 1 | 0.21 | 0.62 | 1.54 | 0.022 | 0.020 | － | 0.35 | 0.015 | 0.0017 |
| Example 2 | 0.23 | 0.65 | 1.58 | 0.020 | 0.030 | － | 0.41 | 0.013 | 0.0022 |
| Example 3 | 0.25 | 0.58 | 1.42 | 0.019 | 0.025 | － | 0.47 | 0.018 | 0.0010 |
Example 1
The molten iron in the embodiment comprises the following components in percentage by mass: c: 4.24%, Si: 0.17 percent, Mn0.12 percent and Cr0.05 percent.
The preparation method of the reinforcing steel bar comprises the following steps: pre-desulfurizing molten iron, adding the molten iron, scrap steel and the like into a converter with the capacity of 120 tons, then carrying out top-bottom combined blowing smelting until the C content in the molten steel is lower than 0.06 percent and the P, S content is lower than 0.045 percent, tapping, adding FeSi, FeMn, FeCr alloy and anthracite into the molten steel to carry out Si, Mn, Cr and C element alloying in the process of tapping to 1/3-2/3, and controlling the Cr content in the molten steel to be 0.35%; after the molten steel reaches a small platform behind the furnace, a steel ladle is immediately connected into a pipeline, argon is blown into the molten steel in the steel ladle, and the argon is blown into the molten steel for 5min, so that various added alloys are fully melted and uniform; the method comprises the following steps of electrically heating a steel ladle after the steel ladle reaches an LF furnace, feeding a proper amount of titanium wires in the early stage of refining of the LF furnace, adjusting Ti to a proper level, feeding a proper amount of boron wires in the later stage of refining of the LF furnace, controlling the content of Ti in molten steel to be 0.015%, controlling the content of B in the molten steel to be 0.0017%, wherein the content of effective boron is more than or equal to 96%, and carrying out component fine adjustment treatment and then conveying the molten steel to a continuous; adopting protective casting when casting into casting blanks of 160mm multiplied by 160mm on a 6-machine 6-flow square billet continuous casting machine, and naturally cooling the casting blank stacks to room temperature; and cooling the casting blank, conveying the casting blank to a continuous bar production line, heating the casting blank in a heating furnace at 1110 ℃ and a soaking temperature of 1150 ℃, heating and soaking for 90min, roughly rolling for 6 times, medium rolling for 6 times, finely rolling for 6 times at 930 ℃, leaving no water to pass through the casting blank after rolling, feeding the casting blank to a cooling bed at 935 ℃, naturally cooling the casting blank to below 200 ℃ on the cooling bed, and finishing and shearing to obtain the phi 12mm hot-rolled ribbed steel bar.
Example 2
The molten iron in the embodiment comprises the following components in percentage by mass: c: 4.31%, Si: 0.19 percent, Mn0.15 percent and Cr0.06 percent.
The preparation method of the reinforcing steel bar comprises the following steps: pre-desulfurizing molten iron, adding the molten iron, scrap steel and the like into a converter with the capacity of 120 tons, then carrying out top-bottom combined blowing smelting until the C content in the molten steel is lower than 0.06 percent and the P, S content is lower than 0.045 percent, tapping, adding FeSi, FeMn, FeCr alloy and anthracite into the molten steel to carry out Si, Mn, Cr and C element alloying in the process of tapping to 1/3-2/3, and controlling the Cr content in the molten steel to be 0.41 percent; after the molten steel reaches a small platform behind the furnace, a steel ladle is immediately connected into a pipeline, argon is blown into the molten steel in the steel ladle, and the argon is blown into the molten steel for 5min, so that various added alloys are fully melted and uniform; the method comprises the following steps of electrically heating a steel ladle after the steel ladle reaches an LF furnace, feeding a proper amount of titanium wires in the early stage of refining of the LF furnace, adjusting Ti to a proper level, feeding a proper amount of boron wires in the later stage of refining of the LF furnace, controlling the content of Ti in molten steel to be 0.013%, controlling the content of B in the molten steel to be 0.0022%, wherein the content of effective boron is more than or equal to 96%, and carrying out fine adjustment treatment on components and then feeding the components to a continuous; adopting protective casting when casting into casting blanks of 160mm multiplied by 160mm on a 6-machine 6-flow square billet continuous casting machine, and naturally cooling the casting blank stacks to room temperature; and cooling the casting blank, conveying the casting blank to a continuous bar production line, heating the casting blank in a heating furnace at 1150 ℃ and 1180 ℃, heating and soaking for a total time of 110min, performing rough rolling for 6 times, medium rolling for 6 times and finish rolling for 6 times at 950 ℃, and naturally cooling the casting blank on a cooling bed to below 200 ℃ without water penetration after rolling, and finishing and shearing to obtain the phi 25mm hot rolled ribbed steel bar.
Example 3
The molten iron in the embodiment comprises the following components in percentage by mass: c: 4.27%, Si: 0.14 percent, Mn0.19 percent and Cr0.07 percent.
The preparation method of the reinforcing steel bar comprises the following steps: pre-desulfurizing molten iron, adding the molten iron, scrap steel and the like into a converter with the capacity of 120 tons, then carrying out top-bottom combined blowing smelting until the C content in the molten steel is lower than 0.06 percent and the P, S content is lower than 0.045 percent, tapping, adding FeSi, FeMn, FeCr alloy and anthracite into the molten steel to carry out Si, Mn, Cr and C element alloying in the process of tapping to 1/3-2/3, and controlling the Cr content in the molten steel to be 0.47%; after the molten steel reaches a small platform behind the furnace, a steel ladle is immediately connected into a pipeline, argon is blown into the molten steel in the steel ladle, and the argon is blown into the molten steel for 5min, so that various added alloys are fully melted and uniform; the method comprises the following steps of electrically heating a steel ladle after the steel ladle reaches an LF furnace, feeding a proper amount of titanium wires in the early stage of refining of the LF furnace, adjusting Ti to a proper level, feeding a proper amount of boron wires in the later stage of refining of the LF furnace, controlling the content of Ti in molten steel to be 0.018%, controlling the content of B in the molten steel to be 0.0010%, wherein the content of effective boron is more than or equal to 96%, and carrying out component fine adjustment treatment and then conveying the molten steel to a continuous; adopting protective casting when casting into casting blanks of 160mm multiplied by 160mm on a 6-machine 6-flow square billet continuous casting machine, and naturally cooling the casting blank stacks to room temperature; cooling the casting blank, conveying the casting blank to a continuous bar production line, heating the casting blank in a heating furnace at the temperature of 1190 ℃, soaking at the temperature of 1220 ℃, heating and soaking for a total time of 150min, performing rough rolling for 6 times, medium rolling for 6 times and finish rolling for 6 times at the temperature of 975 ℃, and not penetrating water after rolling, wherein the temperature of an upper cooling bed is 980 ℃. Naturally cooling to below 200 ℃ on a cooling bed, and finishing and shearing to obtain the phi 32mm hot-rolled ribbed steel bar.
Comparative example
The molten iron in the comparative example comprises the following components in percentage by mass: c: 4.21%, Si: 0.13 percent, Mn0.15 percent and Cr0.05 percent.
The preparation method of the reinforcing steel bar in the comparative example comprises the following steps: pre-desulfurizing molten iron, adding the molten iron, scrap steel and the like into a converter with the capacity of 120 tons, then carrying out top-bottom combined blowing smelting until the C content in the molten steel is lower than 0.06 percent and the P, S content is lower than 0.045 percent, tapping, and adding FeSi, FeMn, VN16 and anthracite into the molten steel to carry out Si, Mn, V and C element alloying when the tapping is carried out to 1/3-2/3; after the molten steel reaches a small platform behind the furnace, a steel ladle is immediately connected into a pipeline, argon is blown into the molten steel in the steel ladle, and the argon is blown into the molten steel for 5min, so that various added alloys are fully melted and uniform; refining and deoxidizing in an LF furnace, desulfurizing, finely adjusting components, and then feeding the product to a continuous casting machine for casting; adopting protective casting when casting into casting blanks of 160mm multiplied by 160mm on a 6-machine 6-flow square billet continuous casting machine, and naturally cooling the casting blank stacks to room temperature; and cooling the casting blank, conveying the casting blank to a continuous bar production line, heating the casting blank in a heating furnace at 1150 ℃ and 1180 ℃, heating and soaking for a total time of 110min, performing rough rolling for 6 times, medium rolling for 6 times and finish rolling for 6 times at 950 ℃, and naturally cooling the casting blank on a cooling bed to below 200 ℃ without water penetration after rolling, and finishing and shearing to obtain the phi 25mm hot rolled ribbed steel bar.
Examples of Effect test
1. Test method
1.1 mechanical property test: refer to GB/T1499.2-2018 Steel for reinforced concrete part 2: hot rolling ribbed bars. The yield strength (Rel), tensile strength (Rm), elongation after fracture (A), total elongation at maximum force (Agt) and yield ratio of the steel bar were measured.
1.2 metallographic structure test: refer to GB/T13298-2015 Metal microstructure inspection method. And (4) determining the metallographic structure composition and ferrite grain size of the steel bar.
1.3 acid-soluble boron test: the method is carried out according to the content of acid-soluble boron and total boron in steel measured by graphite furnace atomic absorption spectrometry. And (4) measuring acid-soluble boron, namely the effective boron content, of the reinforcing steel bar.
2. Test results
Table 2 mechanical properties, metallographic structure and boron content of the reinforcing steel bars of examples 1 to 3 and comparative examples
As can be seen from Table 2, the carbon manganese chromium hot-rolled ribbed steel bar with 400 MPa-level effective boron not less than 96% prepared by the method has the effective boron content not less than 96%, the yield strength not less than 410MPa, the tensile strength not less than 550MPa, the elongation after fracture not less than 25%, the maximum total elongation not less than 13%, the yield ratio not less than 1.30, the microstructure of ferrite and pearlite, the ferrite grain size not less than 11, and meets the requirement of the 400 MPa-level hot-rolled ribbed anti-seismic steel bar. The hardenability can be improved by compounding chromium and effective boron to replace expensive V or Nb microalloy elements to produce 400 MPa-level hot-rolled ribbed anti-seismic reinforcing steel bars, the ferrite grain size is higher than that of comparative steel, the microalloying cost is reduced, and the method has better market competitive advantages.
Claims (8)
1. The carbon manganese chromium hot-rolled ribbed steel bar with effective boron not less than 96 percent is characterized in that: the chemical components by weight percentage are as follows: c: 0.21% -0.25%, Si: 0.50-0.70%, Mn: 1.40-1.60%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Cr: 0.30-0.50%, Ti: 0.010% -0.020%, B: 0.0008 to 0.0030 percent, and the balance of Fe and inevitable impurities.
2. The preparation method of the carbon-manganese-chromium hot-rolled ribbed steel bar with effective boron not less than 96% is characterized by comprising the following steps: pre-desulfurizing molten iron, smelting, alloying, LF refining, continuously casting small square billets, heating steel billets, rolling and cooling to obtain the alloy steel; the titanium wire is fed in the early stage of LF refining, the boron wire is fed in the later stage of LF refining, the content of Ti in the molten steel is controlled to be 0.010-0.020%, the content of B in the molten steel is controlled to be 0.0008-0.0030%, and the effective boron is more than or equal to 96%.
3. The method of claim 2 for producing a carbon manganese chromium hot rolled ribbed bar having an effective boron content of not less than 96%, wherein: the molten iron comprises the following chemical components in percentage by mass: c: 4.00 to 4.40 percent of Si, less than or equal to 0.30 percent of Mn, less than or equal to 0.30 percent of Cr and less than or equal to 0.10 percent of Cr.
4. The method of claim 2 or 3 for producing a carbon manganese chromium hot rolled ribbed bar having an effective boron content of not less than 96%, wherein: and smelting until the C content in the molten steel is less than or equal to 0.06 percent, the P content is less than or equal to 0.045 percent, and the S content is less than or equal to 0.045 percent.
5. The method of claim 2 for producing a carbon manganese chromium hot rolled ribbed bar having an effective boron content of not less than 96%, wherein: the heating temperature of the steel billet is 1100-1200 ℃; the soaking temperature is 1140-1230 ℃; the total time of heating and soaking is 80-160 min.
6. The method of claim 2 for producing a carbon manganese chromium hot rolled ribbed bar having an effective boron content of not less than 96%, wherein: the rolling is performed by 6 times of rough rolling, 6 times of medium rolling and 6 times of finish rolling; the finishing temperature is controlled to be 920-1000 ℃.
7. The method of claim 2 for producing a carbon manganese chromium hot rolled ribbed bar having an effective boron content of not less than 96%, wherein: the cooling is carried out by adopting a cooling bed, the temperature of the upper cooling bed is 920-980 ℃, and the cooling is naturally carried out on the cooling bed to be below 200 ℃.
8. The method for preparing a carbon-manganese-chromium hot-rolled ribbed steel bar having an effective boron content of not less than 96% according to any one of claims 2 to 7, wherein the method comprises the following steps: the specification of the steel bar is phi 12 mm-32 mm.
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